Polyester fiberfill filling material (sometimes referred to herein as polyester fiberfill) has become well accepted as a reasonably inexpensive filling and/or insulating material especially for pillows, and also for cushions and other furnishing materials, including other bedding materials, such as sleeping bags, mattress pads, quilts and comforters and including duvets, and in apparel, such as parkas and other insulated articles of apparel, because of its bulk filling power, aesthetic qualities and various advantages over other filling materials, so is now manufactured and used in large quantities commercially. "Crimp" is a very important characteristic. "Crimp" provides the bulk that is an essential requirement for fiberfill. Slickeners, referred to in the art and hereinafter, are preferably applied to improve aesthetics. As with any product, it is preferred that the desirable properties not deteriorate during prolonged use; this is referred to generally as durability. Hollow polyester fibers have generally been preferred over solid filaments, and improvements in our ability to make hollow polyester fiberfill with a round periphery has been an important reason for the commercial acceptance of polyester fiberfill as a preferred filling material. Examples of hollow cross-sections are those with a single void, such as disclosed by Tolliver, U.S. Pat. No. 3,772,137, and by Glanzstaff, GB 1,168,759, 4-hole, such as disclosed in EPA 2 67,684 (Jones and Kohli), and 7-hole, disclosed by Broaddus, U.S. Pat. No. 5,104,725, all of which have been used commercially as hollow polyester fiberfill filling material. Most commercial filling material has been used in the form of cut fibers (often referred to as staple) but some filling material, including polyester fiberfill filling material, has been used in the form of deregistered tows of continuous filaments, as disclosed, for example by Watson, U.S. Pat. Nos. 3,952,134, and 3,328,850.
Generally, for economic reasons, polyester fiberfilling material, especially in the form of staple, has been made bulky by mechanical crimping, usually in a stuffer box crimper, which provides primarily a zigzag 2-dimensional type of crimp, as discussed, for example, by Halm et al in U.S. Pat. No. 5,112,684. A different and 3-dimensional type of crimp, however, can be provided in synthetic filaments by various means, such as appropriate asymmetric quenching or using bicomponent filaments, as reported, for example, by Marcus in U.S. Pat. No. 4,618,531, which was directed to providing refluffable fiberballs (sometimes referred to in the trade as "clusters") of randomly-arranged, entangled, spirally-crimped polyester fiberfill, and in U.S. Pat. No. 4,794,038, which was directed to providing fiberballs containing binder fiber (in addition to the polyester fiberfill) so the fiberballs containing binder fiber could be molded, for example, into useful bonded articles by activating the binder fibers. Such fiberballs of both types have been of great commercial interest, as has been the problem of providing improved polyester fiberfill having "spiral crimp". The term spiral crimp is frequently used in the art, but the processes used to provide synthetic filaments with a helical configuration (perhaps a more accurate term than spiral crimp) does not involve a "crimping" process, in a mechanical sense, but the synthetic filaments take up their helical configuration spontaneously during their formation and/or processing, as a result of differences between portions of the cross-sections of the filaments. For instance, asymmetric quenching can provide "spiral crimp" in monocomponent filaments, and bicomponent filaments of eccentric cross-section, preferably side-by-side but also with one component off-centered, can take up a helical configuration spontaneously.
Polyester fibers having spiral crimp are sold commercially. For instance H18Y polyester fibers are available commercially from Unitika Ltd. of Japan, and 7-HCS polyester fibers are available commercially from Sam Yang of the Republic of Korea. Both of these commercially-available bicomponent polyester fibers are believed to derive their spiral crimp because of a difference in the viscosities (measured as intrinsic viscosity, IV, or as relative viscosity RV), i.e., a difference in molecular weight of the poly(ethylene terephthalate), used as the polymer for both components to make the bicomponent fiber. Use of differential viscosity (delta viscosity) to differentiate the 2 components presents problems and limitations, as will be discussed. This is primarily because spinning bicomponent polyester filaments of delta viscosity is difficult, i.e., it is easier to spin bicomponent filaments of the same the viscosity, and there is a limit to the difference in viscosity that can be tolerated in practice. Since it is the delta viscosity that provides the desirable spiral crimp, this limit on the difference that can be tolerated correspondingly limits the amount of spiral crimp that can be obtained in a delta viscosity type of bicomponent. Accordingly it has been desirable to overcome these problems and limitations.
Crimpable composite filaments have been disclosed by Shima et at, U.S. Pat. No. 3,520,770, by arranging two different components of polymeric ethylene glycol terephthalate polyesters eccentrically and in intimate adherence to each other along the whole length of the filaments, at least one of the said components being a branched polymeric ethylene glycol terephthalate polyester chemically modified with at least one branching agent having 3 to 6 ester-forming functional groups and at least one of said components being an unbranched polymefic ethylene glycol terephthalate polyester. Shima taught use of such filaments in woven fabrics made of such cut staple filaments. Shima did not teach use of his bicomponent filaments as filling material. Shima did not provide any teaching regarding pillows, nor about filled articles, nor about filling materials.